1. Field of the Invention
The present invention relates to an image capture device and a focus control method.
2. Description of the Related Art
In recent years, according to increase in resolution of a solid-state imaging element such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor, demand for an information device having an imaging function, such as a digital still camera, a digital video camera, a mobile phone such as a smart phone, or a personal digital assistant (PDA) has rapidly increased. The information device having the above-mentioned imaging function is referred to as an image capture device.
In such an image capture device, as a focus control method of focusing on a main subject, a contrast auto focus (AF) method or a phase difference AF method (for example, see WO 2013/047160) is employed. Since the contrast AF method and the phase difference AF method have advantages of their own, an image capture device using both the methods in combination has been also provided (for example, see JP2010-139942A and JP2010-204294A).
It is known that the phase difference AF method has low reliability when a high-frequency subject is present. Thus, JP2010-204294A discloses a technique that determines whether a periodic pattern is present on a subject from analysis of frequencies of normal pixels and performs a focus control by the contrast AF method when the periodic pattern is present.